ceejay i have discovered something about my DSE901s.....take your 901 Atomizer and grab a cotton bud *the one on the stick that you can use to clean out your ears with*
(which you shouldn't do cause you can damage your ear drums) but i do, tsk@me
anyway!, pinch the tip of the cotton bud and make sure it is flat so to get it into a small gap, now push the flat cotton bud into the edge of the thread end of the atomizer and push it in and run it around the outer circle at the battery end of the atomizer
I some times take a tooth pick type tool and lift the round ring circle type part at the battery end of the atomizer and move it about and upwards ....I think sometimes the battery end of the atomizer inside where a little ring type thing is with a black rubber banned underneather, well it is stops touching the battery when you screw the battery on and thats why you start to get very little vapor after some time goes by...this is what i have discovered anyway ....this method that i use often gets my 901's going again......works for me anyway
if you are confused at what i mean, just PM me and i will try to explain it to you a little better...
Let me know how you go